Dim Headlights on 05 379

Discussion in 'Peterbilt Forum' started by jlb7254, Sep 21, 2013.

  1. jlb7254

    jlb7254 Bobtail Member

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    Sep 21, 2013
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    We just got a 05 379 and it has very dim low beams but high beams are ok, High beam indicator light stays on in low beam or high beam. Tried 1 new relay and one side brightened and other side got dimmer, but the indicator light goes off on low beam now. Reversed positions of the two relays and headlights switched sides as to which was bright and which one was dim. Replaced second relay and went back to original problem. What it the correct relay cause I am thinking that could be my problem.
     
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  3. The Admiral

    The Admiral Heavy Load Member

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    I'm just guessing but I would check out my grounds.
     
    Big Don Thanks this.
  4. snowwy

    snowwy Road Train Member

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    my 09 t660 had the wrong bulbs.
     
  5. ‘Olhand

    ‘Olhand Cantankerous Crusty

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    There is a short somewhere--high beam indicator staying on is telling you that--are you hooked to a trailer?
    Check both tailights--then head for fuse box--the fuse boxes on many 379 are notorious for getting moisture in them
     
  6. jlb7254

    jlb7254 Bobtail Member

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    Sep 21, 2013
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    It is not hooked to a trailer, and when I replaced 1 relay the indicator worked as it is supposed to and only 1 headlight was dim on low beam, brights were bright and indicator light came on, when I switch the relays the headlights change sides which one is bright and one is dim. I have cked the grounds and all seem to be fine. I am wondering if I have the right relays in place. And I can see that the fuse panel has gotten wet a few times.
     
  7. The Admiral

    The Admiral Heavy Load Member

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    What do the headlight plugs look like.
     
  8. LBZ

    LBZ Road Train Member

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    Mine was a short in a old trailer that kicked out the low beams. Kept searching through fuses & relays & it turned out to be a fried wire back in the trailer. Check all your grounds truck side or look for a broken wire. Needle in a hay stack I know.

    Also had the right front headlight that was slow to turn on. Checked all connections & added dielectric grease to all terminals to fix that.
     
  9. jlb7254

    jlb7254 Bobtail Member

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    Sep 21, 2013
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    Headlight plugs are new. Looks like the previous owner put them on when he changed to United Pacific bulbs.
     
  10. The Admiral

    The Admiral Heavy Load Member

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    Maybe the previous owner got the wires crossed up or a loose strand of wire is touching something it should not be.
     
    wore out Thanks this.
  11. bubbanbrenda

    bubbanbrenda Road Train Member

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    Bad connection probably ground.
     
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